1. Field of the Invention
In the molded urethane foam marketplace today, there exist two primary production processes--one based on conventional "hot-cure" technology and one based on high resilience (HR) technology. This invention relates to HR foams containing vinylidene chloride polymer, and to the novel polymer/polyol compositions from which they can be produced.
2. Description of the Prior Art
Polymer/polyol compositions suitable for use in producing polyurethane elastomers, foams, and the like, are known materials. The basic patents in this field are the Stamberger patents U.S. Pat. No. 3,304,273 (U.S. Pat. No. Re. 29,118), and U.S. Pat. No. 3,383,351 (U.S. Pat. No. Re. 28,715). The polymer/polyol compositions can be produced by polymerizing one or more olefinically unsaturated monomers dissolved or dispersed in a polyol in the presence of a free radical catalyst. Polymer/polyol compositions have the valuable property of imparting higher load-bearing properties to polyurethane elastomers and foams produced therefrom than are provided by unmodified polyols.
Polymer/polyols containing vinylidene chloride have been disclosed previously. For example, Dewald (U.S. Pat. No. 3,655,553) describes the preparation of polymer/polyols containing vinylidene chloride (but no acrylonitrile) in a polyol or a polyol blend. He employed a low reaction temperature (65.degree. C.) and a semi-batch process. Another example is the Patton et al. (U.S. Pat. No. 3,875,258) disclosure of polymer/polyols containing copolymers of bis(.beta.-chloroethyl) vinyl phosphonate and vinylidene chloride and also polymer/polyols containing copolymers of bis(.beta.-chloroethyl) vinyl phosphonate, styrene, and vinylidene chloride. They employ a high reaction temperature (125.degree.-130.degree. C.) and a semi-batch process. Both Dewald and Patton et al. teach that such polymer/polyols can be utilized in the preparation of polyurethanes having flame retardant properties.
A Ramlow et al. patent (U.S. Pat. No. 3,953,393) teaches the preparation of polymer/polyols containing vinylidene chloride only or copolymers of vinylidene chloride and vinyl acetate or ethyl acrylate or methyl methacrylate in polyols containing added unsaturation. It operates at a temperature below 100.degree. C., in the presence of a free-radical catalyst and a chain transfer agent (such as dodecylmercaptan). It employs a batch process having a typical holding time of 4 to 6 hours. According to its teachings, high reaction temperatures (i.e. greater than 100.degree. C.) do considerable damage to sensitive monomers such as acrylonitrile and vinylidene chloride as well as to the polyols, resulting in colored dispersions. Kuryla (Canadian Pat. No. 735,010) provides a generic teaching of the preparation of urethane foams from isocyanates and polymer/polyol compositions. Among the monomers which this patent discloses as being polymerizable with the polyols are acrylonitrile and vinylidene chloride. In its Examples 17 and 18, the patent specifically discloses polymer/polyol compositions made from acrylonitrile, vinylidene chloride, and a trifunctional polyol made by the addition of 1,2-propylene oxide to glycerol to an average molecular weight of about 3000, and an average hydroxyl number of 56. In its Examples 64 and 65, this patent teaches the preparation of urethane foams from such polymer/polyol compositions and tolylene diisocyanate. The patent generically teaches that flexible urethane foams can be made from polyols having a hydroxyl number of from about 40 to about 70 or more. Neither Ramlow et al. nor Kuryla contains a teaching that fire retardant polyurethanes products can be made from the polymer/polyol compositions which they disclose.
The HR process referred to above continues to gain a dominant proportion of the molded foam market because, compared to the hot mold process, it produces a higher quality product at a lower energy demand. Much of the HR molded foam produced domestically has been based upon an 80:20 blend of TDI and PAPI. (TDI is an 80:20 blend of 2,4-tolylenediisocyanate and 2,6-tolylenediisocyanate; PAPI is a polymeric isocyanate.) HR molded foams produced with this isocyanate blend do not require a flame additive to meet the specifications of Federal Motor Vehicle Safety Standard (FMVSS) No. 302. Current commercial molded high resilience (HR) foams are based, in many cases, upon the isocyanate blend (of tolylene diisocyanates and a polymeric isocyanate) and a polymer/polyol composition derived from acrylonitrile and styrene. A continuous process for the production of acrylonitrile:styrene-polymer/polyol is described in Priest (British Patent Specification No. 1,412,797--Example 7). As far as is known, none of the above-mentioned vinylidene chloride-polymer/polyols have been used commercially in producing molded HR foams.
Substantial industry incentives exist to develop HR molded foam technology based upon a single isocyanate e.g. TDI. The conversion of molders currently employing "hot-cure" technology to HR foam technology based upon TDI is attractive because (1) additional isocyanate tankage is not required, (2) less energy is needed for the process, and (3) existing molds can be converted readily to the HR foam process. However, current molded foams based upon TDI require small concentrations of additive flame retardants to meet FMVSS No. 302 specifications. Generally, flame retardant additives are not stable in resin premixes and must be metered in a separate stream to the foam machine mixing head. Elimination of the special equipment and handling procedures for the additive flame retardant would simplify the use of TDI-based HR molded foam technology in a production operation.